Stairways are as old as architecture itself. The design has seen practically no change since Sir Henry Wotton, a 17th Century English diplomat and writer included architecture among his interests and offered his strictures on the construction of stairs.
For several hundred years, stairways were constructed by joining a plurality of individual treads and a plurality of individual risers to separate stringers. In the early 1940's O'Donnell in U.S. Pat. No. 2,205,859 formed treads and risers with an intervening chamfer from one piece of metal. One form of the O'Donnell stairway, however, required the use of separate tread members having considerable thickness to eliminate part or all of the chamfer space between the tread and the next riser. Further, all forms of the O'Donnell stairway required a special Z-shaped stringer so that the one-piece member could be attached to the stringer. The use of the special Z-shape with its inturned flange severely limited the type of metal stringer that could be used. Thus, use of the stairway in one-supporting wall constructions or stairways requiring integral free-standing handrails was difficult or prohibitively costly.